That's true, but from Skyrim's release in 2011 until today I've got two new rigs, and the one I got before my actual mastered Skyrim without problems. However, Skyrim coded on a 32 bit engine was the real bottleneck, but as mentioned, keeping the game stable 60 FPS will neglect that flaw script wise.
As long as FO4 is capable to utilize at least 4 cores, make use of more then 4-8GB RAM and utilizes 64 bit features, everything's will be golden. The only thing I'm afraid of is that they've limited the engine due to consoles. However, there's no need to fall into panic. It's up to the Mod user to create a stable game when using Mods. Every Mod, may it be as low demanding as possible, can still be one Mod to much on your load order, and as long as you treat your game responsible, everything's going to be fine.
The example you paint I get a load from users that delibaretly use both, scipt extensive and graphical extensive Mods, while there's several statments by a Beth script wizard you shouldn't overencumber your FPS.